Certain rotary machines, such as electrical power generators and electric motors, have portions that are electromagnetically active for the purpose of participating in the generation of electrical power and/or torque, depending on the type/use of machine. These machines can be very large, for example, having diameters on the order of meters and even tens of meters. Such large machines can present challenges in their construction, shipping, and installation, especially where they are constructed in locations remote from manufacturing facilities. Such large machines can also create maintenance challenges when parts of the active portions fail and need to be replaced. Proper cooling is one element of avoiding failures.
Permanent magnet (“PM”) electromechanical machines utilize permanent magnets to convert rotational inputs into electricity or electrical inputs into rotational motion. One example is wind power units (WPUs) that generate electricity from the energy in wind. Generally, a PM generator or motor has three components. A first component, a stator, is a cylindrical housing that contains electrical windings that remain immobile during electricity generation. A second component, a rotor, is a rotatable assembly containing permanent magnets that spin with respect to the stator. The relative movement between the rotor and the stator produces a moving magnetic field, which induces an electrical current in the stator electrical windings, thereby producing electricity. A third component, such as an axle, bearing assembly or other arrangement depending on configuration, rotationally supports the rotor with respect to the stator, enabling the two to rotate relative to each other.
In operation, the interaction of the magnetic fields with the electrical windings generates heat that must be controlled for proper operation of the device. Large PM machines can generate significant heat that can be difficult to manage or requires complex, active cooling systems.